The present subject matter relates to techniques and equipment to adjust the alignment of a vehicle mounted sensor, typically the leading vehicle sensor of an adaptive cruise control system, in part using an image processing type aligner, such as a 3D visual system otherwise used for alignment of the wheels of the host vehicle.
Adaptive cruise control systems provide an adaptive vehicle speed control, based on sensing of another vehicle or target in front of the host vehicle within which the cruise control operates. Cruise control normally controls host vehicle speed to minimize a difference between actual vehicle speed and a driver-set speed. The adaptive speed control senses the presence of a vehicle or the like in front of the host vehicle and adjusts the cruise control algorithm to account for the target preceding the host vehicle, for example to reduce host vehicle speed and maintain a set distance between the vehicles. A number of different types of automobile manufacturers offer such adaptive cruise control as a comfort aid for driving.
Adaptive cruise control (ACC) systems typically utilize a radar or laser sensor or the like to detect the presence of and distance to a target vehicle leading the host vehicle on which the sensor and the ACC system are mounted. Adaptive cruise control sensors are now commonly mounted on motor vehicles, such as cars, trucks, lorries, vans and the like. Such an adaptive cruise control sensor is located to the front of the host vehicle, generally in the front bumper, and directs a radar beam forwardly in the direction of forward motion of the motor vehicle. Based on the return signal, whenever the sensor detects another vehicle in front of and in the path of the host vehicle, which is moving at a speed slower than the speed of the host vehicle, the adaptive cruise control system determines the speed of the leading vehicle from the sensor signal. The control of the adaptive system sets the cruise speed of the host vehicle to the speed of the leading vehicle.
In order for such an adaptive cruise control system to operate properly, the sensor must be aligned with the vehicle thrust line, and implementation of such a system requires accurate alignment of the sensor with that thrust line. It is essential that the sensor axis, and thus the axis along which the sensor emits a radar or laser beam, extends parallel to the thrust line of the vehicle. In certain cases, the axis of the adaptive cruise control sensor may coincide with the thrust line, although in general, the axis of the adaptive cruise control sensor tends to be spaced apart from the thrust line, but must be parallel thereto.
The thrust line of a vehicle is determined by the toe of the rear wheels of the vehicle, and techniques for measurement thereof will be well known to those skilled in the art. It is a line that extends from the point of intersection of the rear transverse axis of the rear wheels and the longitudinal center line of the vehicle, and it extends forwardly of the vehicle at an angle to the center line of the vehicle. The angle that the thrust line makes with respect to the center line of the vehicle is determined by the toe of the rear wheels, and is relatively small.
Devices for aligning the axis of an adaptive cruise control sensor are known. In general, such a device comprises a mirror and a laser beam. An arrangement is provided for mounting the mirror or the laser light beam source forwardly of the vehicle for cooperating, with the other of the source and the mirror, which is mounted on the adaptive cruise control sensor. Typically, the laser light beam source is mounted on the adaptive cruise control sensor, and the source is arranged with its axis, and in turn, the axis at which the light beam is projected, extending parallel to and relatively close to the axis of the adaptive cruise control sensor. In this arrangement, the mirror is mounted on a separate stand or the like in front of the vehicle.
German published patent application DE 19857871 (C1) discloses a device for aligning the sensor of an adaptive cruise control system to the thrust line of the host vehicle. The disclosed device uses a laser source mounted on a frame positioned in front of the automobile, for directing a laser beam onto a mirror provided by the radar sensor perpendicular to the propagation direction of the radar beam. The rear wheels of the automobile have angle sources, which are used for alignment of the frame with the automobile longitudinal axis in conjunction with angle sources at the opposite sides of the frame, with correction of the radar sensor using evaluation of the reflected laser beam.
Where the mirror is the separately mounted element, it is essential that the mirror is aligned with the vehicle such that the mirror extends transversely across the vehicle thrust line, that is to say perpendicular to the thrust line. In general, it is difficult to locate the mirror so that it accurately extends perpendicular to the thrust line. In cases where the mirror is mounted on the adaptive cruise control sensor, the mirror is mounted transversely of the vehicle thrust line, and the laser light beam source is separately mounted. In this later case, the laser light beam source must be located with the axis of the light beam source extending parallel to the thrust line. It is often difficult to accurately align the laser light beam source on a mounting with the beam source axis extending parallel to the thrust line.
It is well known to align the front and rear wheels of a vehicle with alignment devices or systems. Modem wheel alignment systems, providing increased accuracy and ease of use, have relied on visible targets and computer processing of camera images of the wheel mounted visible targets. Such systems are often referred to as 3D image wheel aligner systems. Examples of methods and apparatus involving computerized image processing for alignment of motor vehicles are described in U.S. Pat. No. 5,943,783 entitled xe2x80x9cMethod and apparatus for determining the alignment of motor vehicle wheels;xe2x80x9d U.S. Pat. No. 5,809,658 entitled xe2x80x9cMethod and apparatus for calibrating cameras used in the alignment of motor vehicle wheels;xe2x80x9d U.S. Pat. No. 5,724,743 entitled xe2x80x9cMethod and apparatus for determining the alignment of motor vehicle wheels;xe2x80x9d and U.S. Pat. No. 5,535,522 entitled xe2x80x9cMethod and apparatus for determining the alignment of motor vehicle wheels.xe2x80x9d A wheel alignment system of the type described in these references is sometimes called a xe2x80x9c3D alignerxe2x80x9d or xe2x80x9cvisual aligner.xe2x80x9d An example of a commercial vehicle wheel aligner is the Visualiner 3D, commercially available from John Bean Company, Conway, Ark., a unit of Snap-on Tools Company.
The prior adaptive cruise control sensor alignment devices, including that disclosed in DE 19857871 (C1), have been designed for use with older alignment measurement heads. In view of the increased accuracy and ease of use, it would be advantageous if the 3D type visual aligner systems could be used to also perform alignment of an adaptive cruise control sensor. The prior adaptive cruise control sensor alignment devices, however, do not work with the more modern 3D type visual aligner systems, due to limiting parameters of the 3D visual aligner and/or the sensor itself.
Hence a need exists for an apparatus for use with a visual aligner system, such as used for wheel alignments, to allow the aligner to also perform an alignment of the sensor of the adaptive cruise control system on a host vehicle. There is an attendant need for a method that facilitates the alignment of an adaptive cruise control sensor of a vehicle using a 3D image wheel aligner.
Techniques and equipment are contemplated for aligning an adaptive cruise control sensor or the like mounted on a host vehicle, using two optical adjustment elements and using an image processing type aligner to properly set-up at least one of those elements to perform the sensor alignment.
A sensor alignment method, for example, involves mounting a first one of the optical adjustment elements in alignment with an axis of the adaptive cruise control sensor. As mounted, this element is movable together with the sensor during adjustment of the sensor. The other adjustment element is mounted on a stand. The method also entails mounting two optical targets of the image processing type aligner on the stand. As mounted, the targets are positioned at transversely spaced apart locations, relative to an axis of the adjustment element that is mounted on the stand. The method also involves positioning the stand, with the second adjustment element and the targets, between the front of the host vehicle and the image input device(s) of the image processing wheel aligner. The optical targets are located so as to allow imaging thereof by the aligner, to determine one or more alignment parameters. The aligner system obtains and processes one or more images of the optical targets, and the position of the stand is adjusted, until the axis of the second adjustment element is aligned relative to the thrust line of the host vehicle. Adjustment of the sensor then involves transmitting a beam of light between the two adjustment elements and adjusting the position of the sensor until the beam of light is positioned so as to indicate a desired alignment of the axis of the adaptive cruise control sensor relative to the thrust line of the host vehicle.
In a disclosed example, the alignment of the stand and adjustment element uses data already stored in the 3D image wheel aligner relating to the toe-in angles of the rear wheels of the vehicle and in turn the location of the thrust line. A front toe analysis may be used to determine when an axis of the targets is perpendicular to the thrust line, and thus when the element on the stand is aligned with the thrust line of the vehicle. In the examples, the adjustment elements consist of a laser beam source and a reflector, typically a flat mirror. In such examples, an adjustment method might entail directing light from the laser light beam source at the light reflector, and adjusting the orientation of the adaptive cruise control sensor until the reflector is coincident with the laser light beam from the laser beam light source, for in turn aligning the axis of the adaptive cruise control sensor with the thrust line of the vehicle.
An apparatus useful as the stand in such a process includes a primary support, for positioning between the image sensor(s) of the wheel aligner and the front of the host vehicle. A secondary support is located on the primary support, for carrying either the laser light beam source or the light reflector. In practice, the beam source or reflector on the secondary support co-operates with the other of those adjustment elements, which is associated with the adaptive cruise control sensor on the host vehicle, for aligning the adaptive cruise control sensor axis parallel to the thrust line of the host vehicle. The apparatus also includes a carrier located on the secondary support. The carrier provides mountings for the two optical targets of the image processing wheel aligner at transversely spaced apart locations relative to a longitudinal central axis of the vehicle. The mounting of the targets facilitates alignment of the laser light beam source or reflector mounted on the secondary support, with respect to the thrust line of the host vehicle.
In one example, the secondary support is adapted for mounting the light reflector. Ideally, the light reflector is aligned with the thrust line of the vehicle so that light incident on the light reflector from the laser light beam source is reflected back along its own path, when the laser light beam incident on the light reflector is parallel to the thrust line. In one such example, the light reflector comprises a flat mirror, and the mirror is located on the secondary support with its flat reflecting surface extending transversely of the thrust line of the vehicle. In an example, the secondary support is rotatable about a vertical axis relative to the primary support, for facilitating alignment of the light reflector with the thrust line of the vehicle.
The carrier may be adapted so that the respective targets are rotatable about a horizontal axis for facilitating alignment of the targets with the cameras of the image processing type aligner. In such an example, the carrier comprises an elongated carrier bar. The carrier bar may rotatable about the horizontal axis; or mountings at the end of the bar may allow rotation of the targets about the horizontal axis, to facilitate certain aligner measurements that may be useful in aligning the stand relative to the thrust line of the vehicle.
In the disclosed examples, the carrier locates the respective targets spaced apart by a distance approximately corresponding to the distance the respective targets would be spaced apart if they were located on respective opposite wheels of the vehicle.
Also, the secondary support may be height adjustable relative to the primary support. Furthermore, a mounting means may be provided on the secondary support for carrying the laser light beam source or the light reflector. This mounting means is pivotal about a vertical axis and facilitates pivotal movement of the adjustment element relative to the secondary support, for example, for aligning the element with the carrier (and thus with respect to the targets).
A system for adjusting a sensor, such as an adaptive cruise control sensor on a vehicle, would include the adjustment elements, a stand like one of the examples disclosed in this case, and a visual aligner with its associated optical targets.
Those skilled in the art will recognize that the techniques described herein may be adapted to other applications. For example, the stand and adjustment elements could be used in combination with a visual image processing type system to align other types of sensors, e.g. including other sensors that may now or in future appear at different locations on various types of vehicles.
Additional objects, advantages and novel features of the examples will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following and the accompanying drawings or may be learned by production or operation of the examples. The objects and advantages of the present subject matter may be realized and attained by means of the methodologies, instrumentalities and combinations particularly pointed out in the appended claims.